Bimetal tubing with ferruled ends



July 25, 1950 w. D. FRANCE ETAL 2,516,689

BIMETAL TUBING wm FERRULED Enns Filed sept. 1:5, 1947 1 ,f u L INVENTORSWater D Faancew By 'Maurice SFr-@sieg Patented July 25, 1950 UNITEDlSTATES PATENT, OFFICE nuETAL rvmilrmaaumn ENDS i Application September13, 1947, Serial No. 773,856 4 Claims. (01.138-64)v This inventionrelates to bimetal or composite tubes for use in heat exchangers orsimilar devices and to the method of making the same.

An object of this invention is to improve the structure of bimetal tubesthat is manufactured for use in installations wherein diierent media areemployed, and the tube is made of two different alloys, so as to makethat portion of the 'tube corrosive and erosive resistant to the mediumto which it is exposed. Specically the invention resides in themanufacture of bimetal tubes in which the outer tube is made to apredetermined length and considerably short of the ends of the innertube so as to provide projecting ends of the inner tube over which areassembled ierrules or bushings of the same basic alloy as the innertube, and wherein all parts are mechanically united together into onesolid tube by an expanding operation of the inner tube. Another objectis to provide as a complete article of manufacture a bimetal tube unitwith which metal ferrules are assembled on the tube ends so that theunit can be furnished ready for insertion in the tube plates withouttrimming and without the need for the user acquiring and handling theferrules as separate parts.

Another point of this invention is in the method of manufacture whereinit has been discovered that in expanding the inner tube into the outertube there is a shortening of the overall length of the inner tube.lThis will naturally cause some amount of slippage of the inner tuberelative to the outer tube and the ferrule adjacent the final expandedend of the tube. To compensate for this condition in the expanding ofthe inner tube,

Another object of this invention is to provide .an improved method ofmanufacture for the Fig. l is a longitudinal sectional view of a bimetalor composite tube embodying the invention as it appears in its finishedform.

Fig. 2 is an exploded sectional view showing the parts employed in thecomposite tube and with Lthe end ferrules in position to be receivedover the exposed ends of the inner tube.

- Fig. 3 is a longitudinalsectional view showingr all the parts of thecomposite tube in relative assembled position vand with the tubepositioned in portions of the apparatus employed for expanding andeiiecting a mechanical bond between the .various parts of the compositetube.

Fig. 4`is a sectional view of the composite tube as it appearsvimmediately after the expanding operation.

Fig. 5 is a sectional view of one end of the tube showing it as securedinto a hole or opening in a tube sheet or end plate, and

Fig. 6 is a view similar to Fig. 5 and showing a modified form ofassembly of the tube -into an end plate.

Referring now to the drawing i'n which like reference numerals designatelike parts throughout outer and inner surfaces of the composite tube 1are to be exposed. p

For many types of heat exchangers to which our composite tube will beapplicable, the outer tube i2 will be one of the ferrous alloys whilethe inner tube yli and end ferrules I3 and It will be one of thenon-ferrous alloys. It should be understood, however, that there' areconditions where this selection of alloys for the respective tubes maybe reversed, or where both inner and outer tubes may be of eitherferrous or non-ferrous alloys having different corrosion resistantproperties, and in general the tubes and ferrulesmay be constructed ofany material suitable for resisting the particular corrosive action ofthe fluids or substances to which they are exposed.

The outer tube i2 will be of a predetermined length for reasons thatwill appear later and which length is considerably less than the lengthof the inner tube ii. thus allowing for exposed 3 ends I and I 8 overwhich the end ferrules Il and I4 are telescoped. Fig. 2 shows in ageneral manner the amount that the ends of the outer tube I2 are removedfrom the ends of the inner tube II, thus leaving an exposed end I5 atthe left end of the inner tube, and an exposed end I6 at the right endof said inner tube. The O. D. and I. D. of the ferrules I3 and I4 aredimensloned to be the same as the 0. D. and I. D. ai the outer tube I2,and the axial length of these ferrules I3 and I4 preferably are somewhatshorter in length than the exposed ends I5 and IG of the inner tube aswill be observed in Fig. 3. Also it will be observed that the.positioning of the outer tube I2 to the inner tube II is such that theright exposed end |`6 is o i greater length than the left exposed endI5, for reasons that will be explained Y later.

While Figs. 2 and 3 of the drawingshow the tubes and ierrules to be inspaced relationship relative to each other, it should be understood thatin the preliminary stages, the inner tube I I is dimensioned so as toallow for a free sliding i'lt into the outer tube I2 and end ierrules i3and I4. In general it has been found that in making composite tubes inthe order of one inch size, a clearance of .030" between theo. D. of theinner tube and the I. D. of the outer tube and end ferrules issufficient to produce a free sliding :Bt between the telescoped partsemployed to make the composite tube.

The method and the apparatus by which the various parts are united intoone single tubular structure or composite tube is shown in Fig. 3. Afterthe various parts that make up the assembled tube are positioned asshown in Fig. 3, the tubing is conveyed to an expanding machine, theessential parts only of which are employedfor the expanding operationbeing disclosed in said Fig. 3.

This machine comprises in general a die block Il,- With a throughopening I8, having a countersink 18a within` which is tted a hardenedsupport ring I9, against which the adjacent end of the inner tube II isadapted to abut during the expanding operation of the inner tube. A plugmember 2li of conventional structure is provided on the end of a longpull rod 2| that passes through the entire length of the inner tube andthrough the opening I8 in die block I'I. The opposite end of the pullrod 2| may be attached to any suitable draw-bench mechanism, not shown,for the purpose of pulling the plug 2II through the inner tube II forexpanding the same. The plug 2U is preferably of a double diameterwherein the leading end 22 is of a size to t snugly into the open end ofthe inner tube I I, while the trailing end 23 is of a size for expandingthe inner tube the proper amount into the outer tube I2 and end ferrulesi3 and I4 to create a iirm m'echanical bond therebetween, and alsogiving due the operation of pulling the plug through thev inner tube Ifor purposes oi.' expanding the same, without necessarily reducing itswall thickness, a shortening of the overall length of said inner tube II will result. With this physical change of the length of said innertube Il, but with no change in length of the outer tube I2 and end1errules I3 and I4 will naturally cause a proportionate amount of axialslippage as between the inner tube II and outer tube I2 and rightferrule I4. This added length at the right exposed end Il is to allowfor this reduction in the overall length of the inner tube II, and stillleave a portion of the inner tube exposed and projecting beyond the endof the right ferrule I4 upon completion of the expanding-operation, in amanner as shown in Fig. 4.

In compensating for this slippage as between the inner and outer tubesand I2 and right ferrule I4, the exposed end of the right ferrule Il isabutted' against a resilient member, which may be in the form of ailoating ring plate 24 slidably mounted in a bracket 25 attached to theadjacent face of the die block Il, illustrated in Fig. 3. A plurality ofsockets 26 may be provided in the adjacent face of the die block I1 andannularly arranged about the-support ring I9. A plurality of coilsprings 21 is provided and being individually fitted into eaeh of thesockets 2B with the outer ends of said springs abutted against the innerface of the floating ring plate 24. From this apparatus construction itwill be noted that in the method of manufacture of the composite tubeill, the inner tube il is :Erst abutted against a support ring i9,immovably held in the die block Il and then the outer tube I2 and endferrules I3 and i4 as a imit are abutted against the iioating ring plate25 that is capable of resiliently giving due to the springs 21. As theexpanding plug 20 isV being drawn through the inner tube I in the sameinto a hrm mechanical bond with the outer tube I2 and end ferrules I3and I4, the inner tube l! as a result will contract in length and, ine'eet, be drawn inwardly from the right ferrule il and then cause theouter tube i 2 and right ferrule i4 to move to the right carrying theiioatng ring plate 24 therewith against the inuence of the springs 21.When the expanding operation fn completed the resulting composite tubeiii will be iinished substantially-as shown in Fig. -igwlth portions ofthe inner tube II exposed beyond the ends of the assembled ferrules I3and Il, said ends being designated as |5a and isa. These ends Ia and IGamay subsequently be cut away to the dot-and-dash line 28 (see Fig. 4) soas to bring the ends of the inner tube li iiush with the exposed ends ofthe ferrules I3 and l5.

Fig. 5 shows one form of installation to which our bimetal ferruled endtubes may be assembled, it being considered suiiicient to show only oneend of the tube connection as both ends will be of like construction.The tube Il is assembled to an end plate or tube sheet 29, having anopening 30 of a size to receive the O. D. of the outer tube I2. Withinthis plate opening 39 are provided a series of annular recesses 3|.

The tube is permanently assembled to the tube sheet or end plate 29 by asuitable tool (not shown) that serves to expand the adjacent open end ofthe inner tube II as at 32, the expanding force being usually of acharacter to increase the diameters of the inner tube and thesurrounding ferrule and adjacent end of outer tube I2. The expansiveforce in the inner tube Il should be of a character to cause thematerial of the outer ferrule to be forced into the annular re- Acesses3|. In case the outer tube I2 happens to be made from a comparativelyhard alloy, such chanicall bond and leak-proof the tubes I and endplates 29.

as steel, it is perceived that only a portion of i this tubing will beexpanded into the adjacent unit.

assembling end ferrules at the place where the tube to be assembled intoa heat exchanger Also by reason of the fact that it is only neces# saryto remove the short end portions Ia and IBa or the inner tube by acutting operation to produce the finished tube as shown in Fig. 1, there1s eliminated the problem of mixed scrap which has heretofore been oneof the problems of fabrias shown in Fig. 5. In a composite tube whereinthe outer tube I2 is of a harder ferrous material,

experience has taught that the material of this tube will be onlypartially expanded into the adjacent annular recess 3I surrounding saidtube. whereas the end ferrules I3 and I4 beingusually of a non-ferrousand softer material, the material thereof will expand ,intosubstantially the full depth of the one or more recesses 3| surroundingthe same to assure an adequate me- Joint as between In Fig. 6 is shown amodified form of `joint wherein the composite tube Ilia may be securedinto an end plate 29@ having a flared opening 26a. In fabricating alcomposite tube for this. particular installation, the length of theinner tube Ila will be initially predetermined so that when Ithe'mechanical bond is eiected with the outer. tube and end fer-rules, theexposed ends I5a and I 6a willbe somewhat longer than what would berequired for the Fig. 5 installation (it being understood that for thelatter installation the inner tube is -cut olf ush with the end ferrulesbefore the installation). The reason that these exposed lengths or endsI-5a and I6a are left longer is because of the difficulty of control inthel expanding operation. By leaving a longer length to the exposed endsI5a and I9a of the inner tube, these lengths can then be cut oil to apredetermined length from the ends of the end ferrules to t the requiredneed ofthe Fig 6 installatlon. In assembling the composite tube Illa inthe ilared opening 29a, the inner tube IIa and also the adjacent bushingIIa will be ilrst expanded by a suitable tool in the manner as describedin connection with Fig. 5, and then by another suitable tool flaredoutwardly in the.

manner as shown in Fig.l 6. By reason of the predetermined cut length orexposed end I5a of the inner tube IIa that is exposed beyond the end ofthe outside tube lila and adjacentferrule I3a, even after the end of thecomposite tube is expanded by the rst aring operation,

` the exposed end I5a of the inner tube Ila will be of sufilcient lengthto allow said length Ila to be `further ared over as atv 33 and concealthe exposed end of the flared bushing I 3a, and serve to make a neatjointwith the end plate 29a.

One of the advantages of this invention is' that the entire compositetube I0 can be made and shipped as a unit from the place of manufacturewithout resorting to'any cutting or milling operations of the tube forthe purpose of eating bimetal tubes for the various installations. v

While we have herein described and upon the `drawing shown anillustrative embodiment of the invention and apparatus for producing thesame, it is to be understood that the invention is not limited thereto,but may comprehend other constructions and arrangements withoutdeparting from the spirit of the invention and details of parts.

What is claimed:

-1. As an article-of manufacture, a bimetal tube comprising an innertube `of one alloy and an outer tube of a different alloy extending overthe greater, part of the length of the innerv tube, the

ends of said inner tube projecting beyond the ends of lthe outer tube,ferrules of an alloy comparable 'tov the inner "tube surrounding theexposed ends of aid inner tube and extending over at least the greaterpart of the length of said exposed ends, and said tubes and ferrulesbeing mechanically bondedv together as oneintegral tube unit ready forassembly with a heat exchanger or the like.

. 2. .As an articlev of manufacture, a bimetal tube comprising an innertube of relative soft metal and an outer tube of relatively hard metalextending over the greater part of the length of the inner tube. theends of said inner tube projecting beyond the outer tube, and ferrulesof a metal comparable in hardness to the inner tube. surrounding theexposed ends of said inner tube and extending over atleast the greaterpart of the length of said exposed ends, said tubes and ferrules beingmechanically bonded together as one unit ready for assembly with tubesheets of a heat exchanger or the'lik 3. The bimetal tube dened in claim1 wherein the inner tube extendsslightly beyond the v ferrules at eachend of the finished tube.

4. The bimetal tube defined in claim 1 wherein the.length of theferrules is the same as the length of the exposed ends of the innertube.

WALTER D. FRANCE. MAURICE C. PRESLEY.

REFERENCES CITED The following references are of jrecord in the file ofthis patent:

UNITED STATES PATENTS r2,386,147 als oct. 1e, 1945

